# Why is the Hebrew calendar considered neither lunar nor solar but rather a combination therein? **URL:** \ **Category:** Factual Questions\ **Created:** [January 4, 2012, 10:45am UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369 "2012-01-04T10:45:10Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![andrea\_green](https://avatars.discourse-cdn.com/v4/letter/a/ecccb3/32.png) [@andrea\_green](https://boards.straightdope.com/u/andrea_green)\ **Post date:** [January 4, 2012, 10:45am UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369/1 "2012-01-04T10:45:10Z")
[Wikipedia](http://en.wikipedia.org/wiki/Hebrew_calendar) has some information about the subject and talks about leap years but I find their explanation rather confusing. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [January 4, 2012, 11:24am UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369/2 "2012-01-04T11:24:13Z")
The Hebrew calendar is completely lunar - if you tell me the date, I could tell you the phase of the moon. However, since 12 lunar months is slightly less than a full solar cycle, every few years an extra month is added, so that the seasons don’t go out of whack. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 4, 2012, 12:46pm UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369/3 "2012-01-04T12:46:04Z")
It’s the addition of that extra month that makes it not completely lunar. A comnpletely lunar year starts to go out of phase with the solar year and “drifts” through the solar year, so that what was your summer month eventually gets to be a winter month, then after an equally long time gets to be a summer month again. The Muslim calendar is a truly lunar calendar, with no compensating month added. ---
**Author:** ![andrea\_green](https://avatars.discourse-cdn.com/v4/letter/a/ecccb3/32.png) [@andrea\_green](https://boards.straightdope.com/u/andrea_green)\ **Post date:** [January 4, 2012, 4:19pm UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369/4 "2012-01-04T16:19:36Z")
Follow-up question: So if some jewish years contain leap months, what do jewish people who need to commemorate certain dates that only fall on leap years do? For example, say a parent died during a leap month. I believe jewish people are supposed to go to synagogue and do special prayers every year on the date of their parent’s death. ---
**Author:** ![Bag\_of\_Mostly\_Water](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bag_of_mostly_water/32/1029_2.png) [@Bag\_of\_Mostly\_Water](https://boards.straightdope.com/u/Bag_of_Mostly_Water)\ **Post date:** [January 4, 2012, 4:52pm UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369/5 "2012-01-04T16:52:51Z")
During leap years, a second month of Adar is added. Anything which needs to be observed in Adar II is observed in Adar in non-leap years. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [January 5, 2012, 7:46pm UTC](https://boards.straightdope.com/t/why-is-the-hebrew-calendar-considered-neither-lunar-nor-solar-but-rather-a-combination-therein/608369/6 "2012-01-05T19:46:04Z")
> [@Bag\_of\_Mostly\_Water](#): > > During leap years, a second month of Adar is added. Anything which needs to be observed in Adar II is observed in Adar in non-leap years. And someone who is born early in Adar II will celebrate birthdays in non-leap years sooner than someone born late in Adar I or in an ordinary Adar. But anything that is to be commemorated in Adar II is simply commemorated in Adar in an ordinary year. There are 7 leap years in every 19 year cycle and that is off by about 2 hours in every 19 years or about a day every 2 centuries. AFAIK, there is no provision for correcting that drift. Since the current calendar dates from the early Christian era it has now drifted by about 8 days. Not yet really noticeable, but in another few millenia it is will be.